1. Field of the Invention
This invention relates to a magnetron sputtering apparatus for forming a thin film in vacuum by means of magnetron sputtering and, particularly, a magnetron sputtering apparatus capable of activating the ionization in a plasma to increase the ion current to a substrate.
2. Description of the Prior Art
In a conventional magnetron sputtering apparatus for forming a thin film in vacuum by means of magnetron sputtering, for example, a magnetron evaporation source 34 having an inside magnetic pole 31, a ring-like outside magnetic pole 32 and a target 33 is arranged so as to surround the circumference of a substrate 36 within a vacuum chamber 35, as shown in FIG. 13, and magnetic lines of force 38 is generated so as to successively connect the outside magnetic poles 32 of the adjacent magnetron evaporation sources 34 to surround the circumference of the substrate 36 by the magnetic lines of force 38 by differing the polarities of the respective outside magnetic poles 32 of the mutually adjacent magnetron evaporation sources 34, whereby the plasma generated by a glow discharge is sealed around the substrate 36, and the ionization of a metal atom evaporated from the magnetron evaporation source 34 is activated to form a metal thin film of high density on the substrate 36 (Japanese Patent Publication No. 5-505215; hereby fully incorporated by reference).
However, the conventional method required two types of magnetron evaporation sources with different polarities of an outside magnetic pole 32 and an inside magnetic pole 31 since it is necessary to differ the magnetic poles of the outside magnetic poles 32 of the mutually adjacent magnetron evaporation sources 34 in order to generate the magnetic lines of force 38 so as to successively connect the outside magnetic pole 32 of each magnetron evaporation source 34 to surround the circumference of the substrate 36 by the magnetic lines of force 38.
The shape or intensity of magnetic field was also varied depending on the number or arrangement of the magnetron evaporation sources 34 since the magnetic field for surrounding the substrate 36 was formed only by the magnetic lines of force 38 mutually connecting the magnetic poles 32 of the magnetron evaporation sources 34. In order to provide a desired shape or intensity of magnetic field necessary to sufficiently seal the plasma around the substrate 36, conversely, the number or arrangement of the magnetron evaporation sources 34 was restricted. In a large-sized apparatus for processing a large substrate 36, for example, a number of magnetron evaporation sources 34 had to be arranged since a desired magnetic field can not be obtained unless the mutually adjacent magnetron evaporation sources 34 are arranged within a certain distance.
Further, once the arrangement of the magnetron evaporation sources 34 is determined, the shape of magnetic field is also determined, and it is difficult to change. Although the shape of magnetic field can be changed also in the prior arts by forming the magnetic pole of the magnetron evaporation source 34 of not a permanent magnet but a coil, the arrangement of a plurality of coils in the magnetron evaporation source 34 lead to the problems of the larger size and more complicated structure of the magnetron evaporation source 34.